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Why the acanthomorphs?


Why study acanthomorphs ? Why is this group worthy of interest ? There are many reasons, we will now take you on a tour of a few of them.


A major group

60% of known teleostean species and a third of vertebrates are acanthomorphs. This group includes around 16,000 species, in more than 311 families. However, their large scale classification still retains groups that owe more to traditions than to their real relationships. Like birds, they represent one of the large groups remaining to classify among vertebrates.


A group of culinary interest

Archeological findings show that numerous acanthomorph species have been on the menu for a very long time, in almost all human populations. Cod Gadus morhua (Gadus morhua, Gadidae), for instance, has fed european populations during centuries.

More than 700,000 tons of common mackerel Scomber scombrus (Scomber scombrus, Scombridae), more than 40,000 tonnes of common sole Solea solea (Solea solea, Soleidae), and 40,000 tonnes of red tuna Thunnus thynnus (Thunnus thynnus, Thunnidae) are fished annually.


A group of high ecological importance

Either as preys or predators, Acanthomorphs are present at every level of aquatic food webs. Their eggs, larvae and juveniles feed many aquatic organisms. Some species, like tunas Thunnus thynnus (Thunnus thynus, Thunnidae), swordfishes Xiphias gladius (Xiphias gladius, Xiphidae), and in European freshwaters pike-perches Sander lucoperca (Sander lucioperca, Percidae) are at the top of the trophic webs. Their extinction by overfishing, could destabilise ecosystems and allow the proliferation of organisms like jellyfishes.


A diverse group

  • diverse forms

Acanthomorphs' examples
All these animals are acanthomorphs (Photographs: F. André, G. Dallavalle, V. Maran, A.P Sittler).
  • living in diverse environments

Acanthomorphs living environments
Acanthomorphs are present from abysses to brooks, and from over salted to freezing waters (Photographs: B. and J. Chanet).

A group with a lot still to discover

Each year, more than 300 new acanthomorph species are discovered and described, especially in poorly known and explored ecosystems such as abysses and extreme biotas (Antarctic waters)...

A few of the acanthomorphs species described in 2009:

Enigmatochromis lucanusi Lamboj 2009 (Perciformes, Cichlidae)
Phenacoscorpius longirostris Motomura & Peter 2009 (Scorpaeniformes: Scorpaenidae)
Diancistrus typhlops Nielsen, Schwarzhans & Hadiaty, 2009 (Bythitidae, Ophidiiformes)
Symphurus megaso Lee, Chen, & Shao 2009 (Cynoglossidae, Pleuronectiformes)
Symphurus multimaculatus Lee, Munroe & Chen 2009 (Cynoglossidae, Pleuronectiformes)

Alpha-systematists (see page) work every day on these activities.


A group to understand

Many acanthomorph species present interesting biological traits. Their discovery, study and analysis provide clues and data to understand the living world and even explore new technical applications.

notothenioidNotothenioids (as Trematomus pennellii, on the left) are acanthomorph fishes living in the Southern Ocean around Antarctica. This Ocean is enriched in oxygen but very cold as well, several degrees below zero. The metabolism of the Notothenioids is low, using very active enzymes and anti-freeze molecules present in the blood.  These prevent the formation of ice crystals within tissues and cells. In some species (family Channichthyidae), hemoglobin (the red blood pigment) is absent altogether, as are red blood cells (also referred to as erythrocytes). White gillsTheir blood is colorless and their gills are white, as in Chionodraco hamatus (image on the right).

To learn more about these antarctic fishes: see Lecointre and Ozouf-Costaz (2004 [1]).

The study of the diversification patterns of acanthomorph species, often with closely related species present in close and isolated areas, helps to explore and understand mechanisms for both the origin and the evolution of species.

African lake cichlids  cichlid are very diverse, with around 1,500 species. Their study highlighted evolutionary mechanisms like the relations between successive isolations and important genomic and chromosomic changes.
Similarly, in the European seas, the study of the diversity of several acanthomorph families helps to understand the consequences of the melting of European ice caps and the shaping and isolation of new marine areas.
The geographical distribution of some extant labrids Labrus bergylta (Ballan wrasse, Labrus bergylta, Labridae), and several families of flatfishes like scophthalmids Scophthalmus maximus (turbot, Scophthalmus maximus), pleuronectids Platichthys flesus (European flounder, Platichthys flesus) or needlefishes Belone belone (Belone belone, Belonidae) provides clues to understand the various colonisation and isolation events following a major geological event like the last Holocene glaciation.


Zoogeographic hypothesis of the dispersion of the tribe Labrini
Modified from Hanel et al. (2002).

A group with a story still to tell

Many relationships within the acanthomorphs are far from being understood. Our team works on increasing the knowledge on this aspect (see page). Understanding the evolutionary interrelationships within the group will help us to understand its history (see page) .


References

  1. Lecointre G, Ozouf-Costaz C.  2004.  Les poissons antigel de l'océan Austral. Pour la Science. 320:48-54.